Is it possible to schedule weekly backups rather than daily backups?

From the UI  you can set up the schedule to be during weekends only (Saturday and Sundays).

If you want something more specific you can do the following:

1. Pause the agent protection
2. Create a Powershell script using the new-snapshot command
3. Schedule the Powershell script with Windows task scheduler to run on the date and time you want the backup to happen.

Note: You can check the new-snapshot full syntax here

Thank you, removed the weekday schedule and then schedule a weekend schedule for every 360minutes, so every 6 hours over the weekend.  

Thank you for the link to the Powershell scripts, if it does have to be a single backup once a week, i'll investigate them further.

For which backup you asking.